MediaWiki's UserrightsPage::userCanChangeRights

    public function userCanChangeRights( $user, $checkIfSelf = true ) {
        $available = $this->changeableGroups();
        return !empty( $available['add'] )
            || !empty( $available['remove'] )
            || ( ( $this->isself || !$checkIfSelf ) &&
                ( !empty( $available['add-self'] )
                 || !empty( $available['remove-self'] ) ) );